https://www.antennasdirect.com/cmss_...-sellsheet.pdf
The beamwidth for the Clearstream 4 is 43 degrees. From your location the Toronto signals are at 232 degrees and the Buffalo signals at 160 degrees. That's a range of 72 degrees. If you're pointing in the middle (say about 196 degrees), then the Buffalo signals are pretty far from the center point.
It's always a hassle climbing up on the roof but the best experiment you can do is to re-point your antenna at 160 degrees using a real compass and see what happens. My guess is that since the Toronto signals are pretty strong you will not loose them.
If re-pointing at 160 degrees does not bring in Buffalo solidly then bypass the splitters and run your cable to only 1 television to see what happens.